Added save function for amstrad cpc scr images. No load available yet, and the code was pretty quickly hacked. Thanks to CloudStrife for providing libraw2crtc.

git-svn-id: svn://pulkomandy.tk/GrafX2/trunk@1158 416bcca6-2ee7-4201-b75f-2eb2f807beb1

const.h

@@ -112,6 +112,7 @@ enum FILE_FORMATS
   FORMAT_C64,
   FORMAT_KCF,
   FORMAT_PAL,
+  FORMAT_SCR,
   FORMAT_MISC, ///< Must be last of enum: others formats recognized by SDL_image
 };